In post-industrial countries, the past 30 to 40 years have witnessed dramatic changes in the life course trajectories of young men and women, in both the family sphere (marriage, fertility, relationships with adult parents) and the work sphere (education, work). The proposed research will examine both behavioral and ideational aspects of these life course transformations in a country, Japan, where many of these transformations have not yet occurred, but numerous others have. That the process appears to be still unfolding allows us to examine diffusion aspects of the transformation, along with changes in attitudes and life course behavior. The primary data source for the project is the 2000 National Survey on Family and Economic Conditions, with 4,482 male and female respondents aged 20-49 throughout Japan. This survey, designed by the proposed research team, contains the first multi-domain life history data ever collected on national scale in Japan. There are also innovative approaches to examining the diffusion of novel (or "deviant" depending on one's perspective) life course trajectories. The analyses are clustered in four specific aims that examine 1) behavioral aspects of early life course transitions, 2) potential diffusion pathways, 3) the role of childcare options in the balancing of work and family roles, and 4) attitudinal aspects of early life course transitions.